class Solution {
public:
    int climbStairs(int n) {
        if (n == 1)
            return 1;
        vector<int> dp(n, 0);
        dp[0] = 1, dp[1] = 2;

        for (int i = 2; i < n; i++)
            dp[i] = dp[i - 1] + dp[i - 2];
        
        return dp[n - 1];
    }
};